Saturday, 7 August 2010

Partitioning in modern systems

In the early days of computing, partitioning disk to several volumes was sometimes a good idea. Now, “one disk – one volume” is the most practical way to go.

The original factors and reasoning behind having multiple partitions have much less significance now. The maximum available volume size, limited in FAT16 filesystem, is no longer a factor. Modern filesystems such as NTFS have much smaller clusters for a given volume size, so the loss of space to slack is much less a concern.

There are few exceptions,

  • When an extremely large RAID is involved, a single volume may be impractical because of the backup and the filesystem consistency checking considerations. Last but not least, the read-only data recovery requires a lot of free space same size as the damaged volume; this may be difficult to provide for a gigantic monolithic volume.
  • If multiple operating systems are required with multiple different filesystems, then having several partitions is perfectly justified.

The most common side effects of having multiple partitions are:

  • Free space gets “fragmented” – although the combined free space may be large, the individual partitions would not have enough free space to hold whatever monolithic disk space block is required.
  • If the data is somehow logically grouped (e.g. “OS” and “data” partitions), disk space requirements are hard to predict. Eventually OS would outgrow its designated partition, but the free space from the “data” partition cannot be used.

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